topic QApplication.instance() returns QCoreApplication instance in 3ds Max Programming Forum

QApplication.instance() returns QCoreApplication instance

Anonymous — Thu, 19 Sep 2019 15:16:33 GMT

Hello!

In python, I am trying to get the active QApplication object for Max in order to access top-level information such as the active QScreen, screen geometry, etc.

When I run the tollowing code, I get a QCoreApplication instead of the expected QGuiApplication or QApplication:

QtGui.QGuiApplication.instance()

Is there another method for getting the QApplication?

Re: QApplication.instance() returns QCoreApplication instance

drew_avis — Thu, 26 Sep 2019 18:45:31 GMT

Hi, this is a known limitation, and we will document how to work around it. One solution is to use shiboken2 (included with PySide2) to cast the QCoreApplication to a QApplication, like this:

>>> from PySide2 import QtWidgets
>>> import shiboken2
>>> app2 = shiboken2.wrapInstance(shiboken2.getCppPointer(QtWidgets.QApplication.instance())[0], QtWidgets.QApplication)
>>> app2
<PySide2.QtWidgets.QApplication object at 0x0000020A13D67F08>

Hope that helps,

Drew

Re: QApplication.instance() returns QCoreApplication instance

Anonymous — Thu, 26 Sep 2019 23:05:08 GMT

I will try this out ASAP, I spent a long time searching for exactly this workaround. Thanks!!

Re: QApplication.instance() returns QCoreApplication instance

Anonymous — Sat, 18 Jan 2020 00:09:40 GMT

Thank you for this, it's very helpful.

I'm curious though. Why does this problem not happen with Autodesk Maya 2018 ? Why does the instance() method return the correct PySide2 type in that application ?

Re: QApplication.instance() returns QCoreApplication instance

colbey82 — Tue, 11 Feb 2020 10:35:39 GMT

I'm running Max 2020, but I can't import shiboken2, if I run your code I get the following error:

Traceback (most recent call last):
ImportError: No module named shiboken2

Any thoughts on what's causing this?

Re: QApplication.instance() returns QCoreApplication instance

drew_avis — Tue, 11 Feb 2020 12:09:34 GMT

Shiboken2 is part of the PySide2 module in 3ds Max 2020. Can you try this?

from PySide2 import shiboken2

Hope that helps,

Drew

Re: QApplication.instance() returns QCoreApplication instance

bradley_henke — Thu, 06 Aug 2020 00:01:21 GMT

I'm running into this problem on Maya 2020 as well. I've tried using your work around and it seems to work the first time the function is called; however, it seems to stomp on the qApp variable so that any subsequent calls to

PySide2.QtWidgets.QApplication.instance()

return None.

Do you have any other recommendations? Any chance this can patched on Autodesk's end in the same manner as SideFx? (https://www.sidefx.com/changelog/?journal=&categories=&body=&version=18.0&build_0=366&build_1=366&show_versions=on&show_compatibility=on&items_per_page=)

Re: QApplication.instance() returns QCoreApplication instance

jlmunozYTUDK — Thu, 29 Dec 2022 13:32:55 GMT

Thanks.